Little is known conclusively about what causes brain cancer in children, but research studies are consistently finding links to prebirth pesticide exposure.

A new study finds that children who live in homes where their parents use pesticides are twice as likely to develop brain cancer versus those that live in residences in which no pesticides are used. Herbicide use appeared to cause a particularly elevated risk for a certain type of cancer.

It is well established that many pesticides cause cancer in animals.

This study highlights a new and compelling reason to avoid or limit pesticide use and take necessary precautions during exposure. It also adds to a growing body of research that finds that pesticide exposure -- especially with farm life and pesticide use -- might be contributing significantly to this deadly disease.

Brain cancer is the second most common cancer in children, yet why it develops is not clear. Genetics plays a role in some cases, but researchers believe those not due to associated genes are related to environmental factors and exposures.

The authors explain that "parental exposures may act before the child’s conception, during gestation, or after birth to increase the risk of cancer." Exposures at each time period may trigger different changes that lead to cancers, such as genetic mutations or changes in gene expression or hormone and immune function.

The study evaluated more than 800 fathers and more than 500 mothers that lived in residential areas in four Atlantic Coast states (Florida, New Jersey, New York (excluding New York City) and Pennsylvania). Researchers match and compare every person that is "exposed" to an "unexposed" person of the same age and status. In this case, more than 400 fathers and 250 mothers of exposed children were included.

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Researchers assessed -- through telephone interviews with the mothers -- parental exposure to insecticides, herbicides, and fungicides at home and at work beginning two years prior to their child's birth.

Brain cancer cases in children under 10 years old, diagnosed between 1993 and 1997, were included in the study. The children had participated in the original Atlantic Coast childhood brain cancer study. Their illnesses represented a range of cancers, including astrocytomas and primitive neuroectodermal tumours (PNET). Astrocytomas was associated with herbicide use in this study.

The risk of childhood brain cancer was significantly lower for fathers who washed immediately after the pesticide exposure or wore protective clothing versus those who never or only sometimes took precautions.

The parents assessed in this study were generally in contact with the pesticides through residential exposure, including lawn and garden care.